匕首2：如何注入在@Provides方法中创建的对象？

Question

I've got this:

Bike.java

public class Bike {
    String serial;

    @Inject
    Wheels wheels;

    public Bike(String serial) {
        this.serial = serial;
    }
}

BikeModule.java

@Module
public class BikeModule {
    @Provides
    public Bike provideBike() {
        return new Bike("BIK-001");
    }

    @Provides
    public Wheels provideWheels() {
        return new Wheels("WLS-027");
    }
}

BikeComponent.java

@Component(modules = BikeModule.class)
public interface BikeComponent {
    Bike bike();
}

Now here's the problem: when I call BikeComponent.bike() , I get a bike with the serial BIK-001 , as intended, but the wheels are not injected. However, if I annotate the Bike constructor with @Inject and remove the BikeModule.provideBike() method, the wheels do get injected. So the problem seems to be about injecting an object created within a @Provides method, instead of created by Dagger itself.

Is there a way to tell Dagger to inject a provided object?

Answer 1

Rewrite like this:

public class Bike {

    private final String serial;
    private final Wheels wheels;

    @Inject
    public Bike(String serial, Wheels wheels) {
        this.serial = serial;
        this.wheels = wheels;
    }
}

@Module
public final class BikeModule {

    @Provides
    public static Bike provideBike(Wheels wheels) {
        return new Bike("BIK-001", wheels);
    }

    @Provides
    public static Wheels provideWheels() {
        return new Wheels("WLS-027");
    }
}